FIG. 14 shows the configuration of a prior art progressive conversion reproducing apparatus. Numeral 301 indicates a video signal inputting apparatus of receiving an NTSC video signal from an external system and then converting the signal into digital data capable of being stored in a field buffer. Numeral 302 indicates a field buffer of accumulating two fields of the digital data converted by the apparatus 301. Numeral 303 indicates a pixel information comparing apparatus of comparing on a pixel basis the data delayed by two fields in the apparatus 302 with the data of the present field converted and outputted from the apparatus 301. Numeral 304 indicates a discrepancy pixel number counting apparatus of counting on a field basis the number of the pixels determined as discrepancy by the apparatus 303. Numeral 305 indicates a video filter apparatus which performs a filtering process appropriate for a video image onto the data delayed by two fields in the apparatus 302 and onto the data of the present field converted and outputted from the apparatus 301, and which combines the data and then outputs the result. Numeral 306 indicates a motion picture filter apparatus which performs a filtering process appropriate for motion picture material onto the data delayed by two fields in the apparatus 302 and onto the data of the present field converted and outputted from the apparatus 301, and which combines the data and then outputs the result. Numeral 307 indicates a still image filter apparatus which performs a filtering process appropriate for a still image onto the data delayed by two fields in the apparatus 302 and onto the data of the present field converted and outputted from the apparatus 301, and which combines the data and then outputs the result. Numeral 308 indicates a filter switching apparatus of outputting a filter output result selected from the outputs of the apparatuses 305, 306, and 307. Numeral 309 indicates a progressive video buffer of accumulating the progressive video data selected and outputted from the apparatus 308. Numeral 310 indicates a progressive video outputting apparatus of converting the progressive video data accumulated in the apparatus 309 into the form of a progressive video signal, and of outputting the signal. Numeral 311 indicates an output terminal of outputting the output signal from the apparatus 310 to an external system. Numeral 357 indicates a first repeat field detecting apparatus of comparing the discrepancy pixel number obtained as the output result of the apparatus 304 with a threshold value which is a predetermined absolute value, and of detecting that the field is a repeat field if the discrepancy pixel number is smaller than or equal to the threshold value. Numeral 326 indicates a material determining apparatus of recording a repeat field history which is the history of the detection results of the apparatus 357, and of determining on the basis of the recorded repeat field history whether the above-mentioned video input signal is video-recorded material, material having been 3-2-pulled down from a motion picture, or material obtained from a still image. Numeral 321 indicates an elapsed field counting apparatus of counting, on the basis of the repeat field detection result outputted from the apparatus 357, elapsed fields (the number of) which indicates how many fields have elapsed in the above-mentioned video input signal counted from the repeat field. Numeral 358 indicates a progressive conversion controlling apparatus of controlling the apparatus 308 on the basis of the material determination result from the apparatus 326 and in some cases on the basis of the above-mentioned elapsed fields obtained from the apparatus 321, so as to select a filter appropriate to the input video signal. Numeral 322 indicates an apparatus of controlling the apparatus 309 on the basis of the above-mentioned elapsed fields obtained from the apparatus 321, so as to controlling a timing signal of updating the above-mentioned progressive video buffer provided in the apparatus 309 with the progressive video data selected and outputted from the apparatus 308. These apparatuses constitute a progressive conversion reproducing apparatus.
In such a progressive conversion reproducing apparatus, in many cases, solely the detection of a repeat field serves as a condition of controlling the timing of the filtering process and the combining of the output video images. Accordingly, false detection of a repeat field can cause false conversion such as the use of an inappropriate filter and the combining of video images that are intrinsically not to be combined to each other. Thus, important is the detection accuracy for the repeat field. Nevertheless, in the prior art system, when comparison result between the signal two fields ago and the signal of the present field in the inputted video signal is smaller than or equal to a predetermined absolute value, the field is determined as a repeat field. Accordingly, in a scene having little motion such as the case that motion occurs merely in a part of the image, the number of discrepancy pixels decreases, and hence a problem occurs that even a field which is intrinsically not a repeat field is determined as if a repeat field.
Further, when the video quality of video material generated by the 3-2-pulling down of motion picture material is degraded, that is, when noise is introduced into the video image, the difference in the video images due to the noise causes an increase in the number of discrepancy pixels. In another example, when a three-dimensional noise reduction process is carried out for calculating the difference between the preceding and the following fields so as to reduce the noise, discrepancy decreases in successive fields. Nevertheless, in this case, the number of discrepancy pixels compared with the signal two fields ago in a repeat field where the pixels should intrinsically agree with the former ones is calculated from the video images generated by combining frames which are located before and after the frame of the comparison reference and which intrinsically have different images. This can cause a discrepancy in the images by the amount equal to the change in the images before and after the repeat field, and hence can increase the number of discrepancy pixels. When this increase exceeds the threshold value for the repeat field detection, a problem occurs that even a repeat field is determined as if an ordinary field. In such cases described here that the repeat field detection is not accurately achieved, the repeat field information inputted to the apparatus 326 cannot reflect appropriately the feature of the interlace video image inputted to the apparatus 301, so that the material determination can fail and that material determination and filter control can be difficult to be carried out accurately in the video progressive conversion. This can cause frequent switching of filters and inappropriate selection of a filter. Further, a video image composed in an inappropriate timing can be accumulated in the progressive video buffer and then outputted as a video image. These cause a problem of degradation in the quality of the output video image. See, for example, JP-A-2000-188718. The entire disclosure of JP-A-2000-188718 is incorporated herein by reference in its entirety.
Such a video progressive conversion reproducing apparatus requires accurate material determination and filter control. Nevertheless, in the first repeat field detecting means of the apparatus 357, in a scene having little motion, the number of discrepancy pixels becomes smaller than a predetermined threshold value even in a scene other than repeat fields, and hence repeat fields cannot be identified accurately. Further, in case of degradation in the quality of the video material or in case of the use of three-dimensional noise reduction, video information does not completely agree even in a repeat field where the information should intrinsically agree with the former one. This causes a problem that the number of discrepancy pixels exceeds the predetermined threshold value in the apparatus 357, and that accordingly repeat fields cannot be detected even in video material generated by the 3-2-pulling down of motion picture material. In such cases described here that the repeat field detection is not accurately achieved, material determination and filter control become difficult to be carried out accurately in the video progressive conversion. This can cause frequent switching of filters and inappropriate selection of a filter. These cause a problem of degradation in the quality of the output video image.
That is, there is a problem that errors occur in the detection of repeat fields in case of a scene having little motion, in case of degradation in the quality of video material, in case that noise on the time axis is introduced owing to the use of three-dimensional noise reduction, or in case that the video is recorded in irregular patterns.